While many people tend to think of equine arthritis as a senior horse problem, the condition can affect horses of any age.

Sport horses are at higher risk of arthritis due to the nature and intensity of their work. It is estimated that up to 60% of all lameness in horses stems from arthritis or joint disease. [1]

Arthritis is defined as inflammation in one or more joints, which leads to pain and stiffness. The condition is degenerative, meaning it cannot be reversed in most cases and tends to worsen over time.

However, there are steps that horse owners can take to lessen symptoms and also slow the progression of the disease.

Detecting equine arthritis early and managing your horse appropriately are both keys to getting inflammation under control. In many cases, by the time a horse is lame, the arthritis is already advanced.

Managing arthritis relies on treatments that alleviate pain and reduce the progression of the disease. Anti-inflammatory pharmaceuticals and nutritional supplements can be beneficial for alleviating symptoms and improving mobility and quality of life.

Feeding programs that provide omega-3 fatty acids like EPA and DHA can also support joint health, improve comfort and help your horse return to soundness.

Submit your horse’s diet online for assessment by our equine nutritionists and for suggestions on supporting joint health and managing symptoms of arthritis.

Normal Joint Function in Horses

To understand how arthritis affects a horse, it is important to first understand the anatomy and function of healthy equine joints.

Joints are where two or more bones meet in the body, allowing for movement. Horses have three types of joints:

  1. Synovial joints: These types of joints include the knee, fetlock and hock. Cartilage covers the ends of the bones. The joints consist of a synovial cavity filled with lubricating and shock-absorbing synovial fluid between the bones.
     
    The synovial fluid is contained within the joint capsule. These joints allow for flexion, extension and rotation as with ball and socket joints.
  2. Fibrous joints: Less common than synovial joints, fibrous joints do not allow for movement between bones. An example would be the joints between bones in the horse’s skull.
  3. Cartilaginous joints: Occurring where bones are connected by cartilage, these joints allow limited movement and provide shock absorption. The joints between the vertebrae in the horse’s spine are an example of cartilaginous joints.

Arthritis can occur in both synovial and cartilaginous joints but it is most commonly diagnosed in the synovial joints of the leg.

Types of Arthritis in Horses

Three main forms of arthritis can occur in horses: osteoarthritis, traumatic arthritis, and septic arthritis.

All three forms have different root causes and can vary in severity. As a result, they may require different types of treatment.

Osteoarthritis (OA)

OA is the most common form of arthritis and cause of lameness in horses. This condition is also known as degenerative joint disease.

Osteoarthritis can be triggered by:

  • Everyday wear and tear
  • Repetitive motions; especially those involving excessive force
  • Poor conformation

OA involves chronic, progressive, and painful degeneration of the articular cartilage, subchondral bone thickening (sclerosis), osteophytes (small bony growths), and synovial inflammation. [2]

It can affect any joint, but most commonly affects the hocks, knees, stifles, and fetlocks.

Traumatic Arthritis

Many horses develop arthritis in a joint after sustaining an injury in the area. Traumatic arthritis involves inflammation of the synovial membrane and joint capsule, leading to gradual loss of cartilage.

Also known as post-traumatic osteoarthritis (PTOA), the condition is often caused by fractures, articular cartilage lesions, ligament tears or ruptures, cartilage tears, or a combination of these injuries. [3]

Septic Arthritis

Septic arthritis differs from OA and PTOA in that it is caused by the penetration of microorganisms into the joint. It most often develops after intra-articular injections, wounds, or surgery, and commonly involves the hock joint. [4]

Septic arthritis tends to worsen rapidly, leading to extreme lameness. However, the severity of this condition is often linked with the horse’s age, immune status, and the type or amount of infective microorganisms.

Septic arthritis is a serious condition that warrants immediate veterinary attention. The survival rates tend to be lowest for foals but higher in adult horses. The prognosis for adult horses is influenced by the cause of the disease, duration of infection, presence of additional lesions, as well as the treatment protocol.

Studies show that horses treated aggressively during the first 24 hours after onset have the most positive outcome. However, septic arthritis also comes with possible complications such as laminitis, tendonitis, and osteoarthritis, which may limit the horse’s future career. [4]

Symptoms of Equine Arthritis

Horses in the very early stages of arthritis often don’t show symptoms. As the condition progresses, the most common symptoms include:

  • Stiffness
  • Pain, warmth, and swelling of joints
  • Tenderness in affected limb
  • Reluctance to exercise
  • Back pain
  • Slight edema (swelling) of lower leg
  • Loss of appetite
  • Gait abnormalities

Symptoms tend to worsen over time, especially if the condition is left untreated.

Diagnosing Arthritis in Horses

Diagnosing arthritis is not always easy, especially in the early stages when horses may not show symptoms or may only show very mild symptoms.

In fact, the inability to detect early changes has significantly hindered the development of effective therapies. [5]

A variety of imaging techniques, as well as synovial fluid analysis, can help veterinarians diagnose arthritis in horses. [6]

Radiography

This is the most commonly used diagnostic tool for detecting arthritis. X-rays can identify bone chips or bony growths in the joint.

X-rays can also identify narrowed spaces between joints, which are associated with a breakdown of articular cartilage.

However, radiography often does not show early changes in joints. It is more useful when the disease has progressed to a certain point.

Computed Tomography (CT Scan)

This diagnostic tool takes multiple X-ray images at different angles across the limb while the horse is anesthetized. It produces a series of “sliced” images which provide detailed pictures of the structure and shape of the bone.

CT also provides information on bone density which can be helpful in the diagnosis of arthritis.

Arthroscopy

This technique is more invasive than radiography or computed tomography, but is considered the gold standard for detecting changes in cartilage. [6]

Arthroscopy involves the insertion of a small endoscope into the joint, allowing a clear view inside that joint. It is also helpful for detecting joint capsule and intra-capsular lesions. [6]

Nuclear Scintigraphy (Bone Scan)

This diagnostic tool can be used to detect inflammation in joints. It involves using a radioactive dye that is injected into the horse’s bloodstream where it diffuses out of the blood vessels and concentrates in areas of inflammation.

The dye can then be viewed with a special camera.

Ultrasound

This tool is useful for evaluating damage to soft tissue in and around joints, including ligaments and tendons. It does not, however, show problems associated with bone or the joint itself.

Biomarkers

Biomarker analysis has been useful in early diagnosis of arthritis or joint disease. A biomarker is a substance that is measured and used to indicate the status of a metabolic process inside the horse’s body.

For example, biomarkers in synovial fluid and blood serum can be measured to detect changes in the joint. Levels of prostaglandin E2 (PGE2) in synovial fluid indicate the amount of inflammation in the joint. [7]

Treatment of Equine Arthritis

Because arthritis cannot be reversed in most cases, the primary goal of treatment is to reduce inflammation and manage pain to make your horse more comfortable.

In horses with early osteoarthritis, therapeutic strategies aim to preserve tissue structure and function to prevent further damage. [2]

The most commonly used treatments for equine arthritis include corticosteroids, nutraceuticals, non-steroidal anti-inflammatory drugs (NSAIDs), and joint injections.

Oral medications are easy to administer and often effective at managing pain. However, long-term use of corticosteroids or NSAIDs can result in side effects. Several advanced technologies show promise for treating osteoarthritis.

For septic arthritis, treatment involves targeting the infective microorganisms. Antibiotics are often given for two to four weeks. Lavage of the infected joint is also commonly performed by veterinarians. [8]

NSAIDs

Non-steroidal anti-inflammatories drugs, such as phenylbutazone (bute), have long been used to manage pain associated with equine arthritis.

This class of drugs is effective for controlling short-term flare-ups, but negative side effects can occur with long-term use. Traditional NSAIDs alone are not an ideal solution for long-term management of equine arthritis.

A newer type of selective NSAID, firocoxib (Equioxx), works differently from traditional NSAIDs by blocking COX-2 enzymes instead of COX-1. Firocoxib is associated with fewer side effects and is less irritating on the gastrointestinal tract.

Studies have shown that firocoxib is as effective as bute in reducing lameness associated with arthritis and may lead to greater improvement in range of motion. [7] Because of this, firocoxib may be a better option for long-term pain management associated with OA.

Topical NSAIDs are another alternative to traditional NSAIDs. Diclofenac sodium (Surpass) can be applied directly to affected joints. This medication has low systemic absorption, which means there are fewer potential gastrointestinal side effects compared to oral NSAIDs like bute.

Intra-Articular Injections

Intra-articular injections are administered directly into the joint by a veterinarian. They contain hyaluronic acid, polysulfated glycosaminoglycans, or corticosteroids.

This is a commonly used treatment for arthritis, but horse owners should be aware that this type of injection carries some risk. Adverse reactions can include joint inflammation, infection, and septic arthritis.

Regenerative Medicine

Certain naturally occurring products taken from the horse’s body can also be injected into the joint. Regenerative medicine has the potential to prevent further cartilage damage and possibly reverse the damage.

The following are all forms of regenerative medicine used to treat joint disease in horses:

  1. Autologous Conditioned Serum (ACS) is the liquid portion extracted from the horse’s own blood and processed to increase concentration ofcytokines and growth factors.
     
    ACS is a source of beneficial anti-inflammatory mediators, most notably interleukin-1 receptor antagonist protein (IRAP). Clinical studies report improved synovial membrane health, stimulation of natural IRAP production, and improvements in lameness scores in horses treated with ACS. [9]
  2. Platelet—Rich Plasma (PRP) is blood plasma that is filtrated to contain a higher concentration of platelets than whole blood. Used in tendon and ligament injuries as well, PRP is regularly administered to treat joint disease. [10]
  3. Autologous Protein Solution (APS) Marketed under the name Pro-Stride, this product combines the technology of both ACS and PRP. The horse’s own blood is used to make a solution rich in white blood cells, platelets, and serum proteins that are injected into the joint.
     
    One study indicated that intra-articular injection of APS significantly improved lameness and joint range of motion in horses with mild joint disease. [11]
  4. Mesenchymal Stem Cells (MSCs) are adult stem cells derived from fat or bone marrow. Stem cell treatment has been used in soft tissue injuries for some time to regenerate and repair damaged tissue.
     
    Recently, veterinarians have begun using stem cells to treat equine arthritis with some encouraging preliminary data. More research is needed to understand whether MSCs will match the success of other forms of regenerative medicine in treating equine osteoarthritis. [12]

Extracorporeal Shockwave Therapy (ESWT)

This treatment involves directing energy waves at a specific site on the horse’s body. One study showed that ESWT treatment improved lameness and indicators of joint disease. [13]

However, more research is needed to assess the effectiveness of this treatment compared to other common treatment options.

Surgery

For severe cases of arthritis in which there is no other way to alleviate a horse’s pain, fusing a joint via chemical, laser, or physical surgery can help.

With the source of friction removed, pain is diminished and some horses may even be sound enough for riding. [14]

Nutritional Support of Joint Health

A number of oral nutraceuticals are supplemented to support equine joint health.

The most popular ingredients for equine joint health include glucosamine and chondroitin sulphate.

These are substances found naturally in joints that help to repair cartilage and ease inflammation. However, their effectiveness as oral supplements has not been adequately demonstrated in research trials involving horses. [15]

Other supplement ingredients, such as MSM, hyaluronic acid and DHA, are supported by research. Some newer supplements contain soybean and avocado unsaponifiables (ASU) which may reduce inflammation and protect cartilage. [16]

Vitamin and Mineral Supplementation

Like all tissues in the horse’s body, healthy joints rely on adequate nutrition to support tissue growth and maintenance.

Nutrient deficiencies can impair metabolic processes and enzyme systems that are required for joint function and repair. Key vitamins and minerals for joint health include:

  • Zinc and copper: These trace minerals affect cartilage remodelling; deficiencies can affect joint health in growing horses [17]
  • Manganese: This trace mineral is an important co-factor for enzymes that synthesize glycosaminoglycans (GAGs) such as chondroitin sulfate and hyaluronan [14]
  • Selenium, Vitamin E & Vitamin C: These are antioxidants that act throughout the body to neutralize free radicals produced during normal metabolic processes. Antioxidants limit oxidative damage in tissues, including joints
  • Sulfur: This macromineral is an important component of glucosamine and collagen, helping to maintain healthy connective tissue and cartilage.
     
    Supplementation with the natural compound MSM (methylsulfonylmethane) provides a highly bioavailable form of sulfur to support joint health
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  • Cartilage & connective tissue
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When selecting a vitamin and mineral supplement for your arthritic horse, it is important to ensure that nutrients are provided in sufficient amounts and that mineral levels are balanced.

Studies have also shown that supplementation with organic/chelated minerals is more effective for joint health than inorganic minerals. [18] Organic trace minerals are better absorbed and utilized by the horse’s body.

Mad Barn’s Omneity Premix is a balanced vitamin and mineral supplement for horses that contains 100% organic trace minerals, 1,000 IU of vitamin E and 360 mg of ascorbic acid (vitamin C) per serving.

Omneity is formulated to balance the majority of forages and grain-based diets in North America, covering the most common nutritional gaps in the equine diet. If your horse is not already on a complete mineral and vitamin supplement, this is the most important step before considering other joint health supplements.

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  • Complete B-vitamin fortification
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Omega-3 Fatty Acids

Omega-3 fatty acids are well-recognized for their health-boosting effects in both humans and horses. These essential polyunsaturated fats cannot be made in the horse’s body and must be supplied by the diet.

Studies show that supplementing with certain omega-3’s can help to reduce inflammation and relieve symptoms of arthritis in horses. [20][21]

But not all omega-3s are equally effective. Alpha-Linolenic acid (ALA) is a plant-based omega-3 fatty acid that is found in flax, canola, soy, and camelina oil. It must first be converted into longer-chain polyunsaturated fatty acids to promote a physiologic effect.

The omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have high bioavailability and can increase levels of these natural anti-inflammatory compounds in synovial fluid of horses. [19]

Feeding horses EPA and DHA was shown to increase stride length and reduce inflammatory biomarkers in horses with arthritis. [24] In another study, supplementing with DHA-rich microalgae resulted in a reduced inflammatory response and improved lameness scores in horses with joint inflammation. [23]

Mad Barn’s W-3 Oil provides 1500 mg of microalgal DHA and 1500 IU of natural vitamin E per serving to support joint health, mobility and normal regulation of inflammatory pathways.

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Polysulfated glycosaminoglycans (PSGAGs) and Hyaluronan (HA)

These two compounds occur naturally in the synovial fluid and cartilage of healthy joints. Formulations with PSGAGs and Hyaluronan (hyaluronic acid) can be given intramuscularly, intravenously, or intra-articularly. They are meant to supplement or replace naturally occurring compounds lacking in an arthritic joint.

Although more expensive, these treatments are popular due to the ease of administration and low risk of adverse effects.

Long-Term Management of Horses with Arthritis

Appropriate management of your arthritic horse can help to keep inflammation in check and slow the progression of joint deterioration.

For example, managing your horse’s weight can be a key factor in keeping him more comfortable. Overweight horses have more stress on their joints and often have systemic inflammation which may impact joint health. [22]

Follow this guide to correctly Body Condition Score your horse and determine whether he is at a healthy weight.

Providing an appropriate forage source for your horse and minimizing grains and excess carbohydrates in the diet can also help reduce inflammation.

Movement is also beneficial for arthritic joints. Keeping a horse stalled for too much time can have a negative impact on joint health.

Plenty of turnout and light daily exercise is often helpful for horses with arthritis and may help decrease stiffness and inflammation. [14]

When it comes to arthritis treatments, horses may respond differently to various therapies. Often, a combination of treatment modalities is the best approach.

Preventative strategies should be adopted early to help to keep your horse’s joints healthier in the long run. For assistance in designing the right feeding plan for your arthritic horse, submit your horse’s information online and our equine nutritionists will provide you with a complementary review.

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References

  1. Caron, J.P. and Genovese, R.L. Principles and Practices of Joint Disease Treatment. IN: Diagnosis and Management of Lameness in the Horse. Saunders. 2003.
  2. Yangzi, J. and Tuan, R. Origin and function of cartilage stem/progenitor cells in osteoarthritis. Nat Rev Rheumitol. 2015.
  3. Kajabi, A.W., et al. Evaluation of articular cartilage with quantitative MRI in an equine model of post-traumatic osteoarthritis. J Orthop Res. 2021.
  4. Schneider, R.K. et al. A retrospective study of 192 horses affected with septic arthritis/tenosynovitis. Equine Vet J. 1992.
  5. Castanheira, C. et al. Equine synovial fluid small non-coding RNA signatures in early osteoarthritis. BMC Vet Res. 2021.
  6. Arican, M. et al. Diagnostic techniques for the carpal and fetlock joints in horses with arthritis. Medycyna Weterynaryjna. 2019.
  7. Donnell, J.R. and Frisbie, D.D. Use of firocoxib for the treatment of equine osteoarthritis. Vet Med (Auckl). 2014.
  8. Carstanjen, B. et al. Septic arthritis in adult horses. Pol J Vet Sci. 2010.
  9. Frisbie, D.D. et al. Clinical, biochemical, and histologic effects of intra-articular administration of autologous conditioned serum in horses with experimentally induced osteoarthritis. Am J Vet Res. 2007.
  10. Garbin, L.C. and Olver, C.S. Platelet-Rich Products and Their Application to Osteoarthritis. J Equine Vet Sci. 2019.
  11. Bertone, A.L. et al. Evaluation of a single intra-articular injection of autologous protein solution for treatment of osteoarthritis in horses. Am J Vet Res. 2014.
  12. Broeckx, S.Y. et al. The use of equine chondrogenic-induced mesenchymal stem cells as a treatment for osteoarthritis: A randomised, double-blinded, placebo-controlled proof-of-concept study. Equine Vet J. 2019.
  13. Frisbie, D.D. et al. Evaluation of the effect of extracorporeal shock wave treatment on experimentally induced osteoarthritis in middle carpal joints of horses. AVMA. 2009.
  14. Malone, E.D. Managing Chronic Arthritis. Vet Clin Equine. 2002.
  15. Moreira, J.J. et al. Oral glucosamine and chondroitin sulfate on synovial fluid biomarkers from osteoarthritic equine joints. Clinic and Surgery. 2019.
  16. Kawcak, C.E. et al. Evaluation of avocado and soybean unsaponifiable extracts for treatment of horses with experimentally induced osteoarthritis. Am J Vet Res. 2007.
  17. Vidal, G.H. et al. Effects of Copper and Zinc on Cathepsin B Activity in Equine Articular Chondrocytes. J Anim Vet Adv. 2009.
  18. Millican, A. et al. The effects of an intra-articular inflammatory insult on synovial fluid trace mineral concentrations in growing horses fed inorganic or complexed trace minerals.. J Anim Sci. 2018.
  19. Christmann, U. et al. Dynamics of DHA and EPA supplementation: incorporation into equine plasma, synovial fluid, and surfactant glycerophosphocholines. Metabol. 2021.
  20. Manhart, D.R. et al. Markers of Inflammation in Arthritic Horses Fed Omega-3 Fatty Acids. The Prof Anim Sci. 2009.
  21. Ross-Jones, T.N. et al. Influence of an n-3 long-chain polyunsaturated fatty acid-enriched diet on experimentally induced synovitis in horses. J Anim Physiol Anim Nutr (Berl). 2016.
  22. Vick, M.M. et al. Relationships among inflammatory cytokines, obesity, and insulin sensitivity in the horse. J Anim Sci. 2007.
  23. Brennan, KM. et al. The effect of dietary microalgae on American Association of Equine Practitioners lameness scores and whole blood cytokine gene expression following a lipopolysaccharide challenge in mature horses. J Anim Sci. 2017.
  24. Hess, T. and Ross-Jones, T. Omega-3 fatty acid supplementation in horses. R Bras Zootec. 2014.